Firefighters were deployed to battle blazes spreading on the outskirts of the Amazonian basin near the eastern town of Robore, Chiquitos Province, on Monday.
Some 3,800 square miles (9,800 sq. km) are affected by the fires, twice the area estimated on Thursday, 22 August.
Bolivian President Evo Morales announced on Sunday that he is suspending his campaign for re-election to tackle the wildfires at a news conference, where he also welcomed international aid and called for regional cooperation.
A record number of fires have been raging through the Amazon rainforest, the majority of which is located in Brazil, but which also stretches into Peru, Colombia, Ecuador, Venezuela, Bolivia, Guyana, French Guiana and Suriname.